WO2016026856A1

WO2016026856A1 - Metal effect pigment paste comprising a phosphate ester and method of producing a metal effect pigment paste comprising a phosphate ester

Info

Publication number: WO2016026856A1
Application number: PCT/EP2015/068944
Authority: WO
Inventors: Georg TÖNNISSEN; Tat Man TSANG
Original assignee: Eckart GmbH
Current assignee: Eckart GmbH
Priority date: 2014-08-18
Filing date: 2015-08-18
Publication date: 2016-02-25
Anticipated expiration: 2017-02-18

Abstract

The present invention refers to a metal effect pigment paste providing an improved storage stability and improved optical properties. Furthermore, the present invention refers to the method for producing said metal effect pigment paste and the additive used.

Description

METAL EFFECT PIGMENT PASTE COMPRISING A PHOSPHATE ESTER AND METHOD OF PRODUCING A METAL EFFECT PIGMENT PASTE COMPRISING A PHOSPHATE ESTER

The present invention is directed to metal effect pigment pastes used, for example, in solvent borne coatings, as well as their preparation.

Metal effect pigment pastes are known for a long time. They are usually offered with a content of metal pigments of 60 wt.-% to 70 wt.-% in solvents such as white spirit or solvent naphtha. These solvents originate from the milling process called Hall process, wherein metal powder is comminuted in these solvents using fatty acids such as oleic acid, stearic acid or mixtures thereof as grinding aid. Such grinding aids are present in every milled metal effect pigment paste in amounts of typically 0.3 wt.-% to 2 wt.-%, based on the metal pigment.

These fatty acids seem to stabilize the metal pigment pastes and are usually compatible to most coating systems typically used. However, unsaturated fatty acids tend to polymerize to a certain degree when the metal effect pigment paste is stored for some time. This polymerization leads to agglomerates which may render the paste completely unusable. Herein, this problem is especially severe if the metal pastes are, for example, transported in drums by shipping being exposed to sun light leading to temperatures of about 50 °C or even higher inside the drums. Using only saturated fatty acids as grinding aids leads to leafing products that cannot be used in most conventional applications such as automotive coatings.

Prior to their use in solvent borne coatings or in aqueous coatings the metal pigments need to be dispersed in a slurry. This dispersion needs to be done with great care to prevent damaging the platelet-like metal effect pigments.

Regarding aqueous formulations many ways have been researched to stabilize metal pigments against gassing using, for example, organic phosphonic acids of phosphoric acid or esters thereof. These compounds, however, do not necessarily improve the storage stability of the pastes. There is a need to overcome this problem.

US 2014/0076201 A1 discloses the use of functionalized phosphonic acids to stabilize metal pigments in aqueous formulations. However, the phosphonic acids described therein are difficult to synthesize and unusable in solvent borne coatings.

EP 934365 B1 discloses a process for preparing a low-or non-dusting substantially nonvolatile metal flake pigment composition, which comprises ball milling atomised metal powder in a milling fluid substantially comprised of water in the presence of one or more corrosion inhibitors and a substance which acts as a lubricant for the milling process. The applications of the paste or granules containing metal effect pigments are dealing with aqueous applications.

WO 2013135831 A1 discloses an effect pigment paste suitable for solvent borne systems comprising a wax, three different binder materials and a thickener. This paste exhibits enhanced storage stability. However, such a multicomponent systems are difficult to handle and it is typically very difficult to ensure compatibility with many formulations.

EP 0 256 427 discloses the use of dispersing additives based on phosphoric acids of ethoxylated fatty alcohols for pigments in aqueous formulations, especially for the cosmetic sector.

Although, the currently available metal effect pigment pastes using non polar solvents provide a certain storage stability there is still the need to increase said storage stability in a preferably very simple and effective manner. In this context, the metal effect pigment pastes should preferably not suffer from yellowing. Furthermore, the optical properties such as flop or brightness of the pigments should not decrease significantly compared to conventional metal effect pigment pastes with fatty acids. Preferably the optical properties should not decrease at all.

The problem has been solved by a metal effect pigment paste, wherein the metal effect pigment paste comprises:

A) 55 to 70 wt.-% metal effect pigments, based on the total weight of the metal effect pigment paste, with a d₅o-value in the range of 5 μηη to 80 μηη

B) 0.2 to 10 wt.-% of at least one additive according to formula (I), based on the weight of the metal effect pigments,

wherein the R¹ are independently from each other selected from C9-C30 aliphatic groups, Alk is selected from the group consisting of ethoxy, propoxy and mixtures thereof, the R² are independently from each other selected from the group consisting of H, C1 -C4 alkyl groups and cationic counter ions,

n is a number in the range of 3 to 100 and represents the number averaged value of the number of alkoxy units, x is 1 or 2,

C) at least 23 wt.-%, based on the total weight of the metal effect pigment paste, of at least one solvent, wherein at least 80 wt-% of the solvents are selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof, based on the total weight of the solvents.

It has to be understood that if R² is a cationic counter ion the corresponding structural element (OR²) is a combination of an O^" anionic group covalently bound to the additive according to formula (I) and the cationic counter ion. Examples of cationic counter ions are alkali ions, earth alkali ions or ammonium ions like (NH₄)⁺ and C1 -C10 alkyl ammonium groups. A specifically preferred group of the C1 -C10 alkyl ammonium groups are C1 -C10 alkyl ammonium groups with 1 , 2 or 3 alkyl groups independently from each other selected from C1 -10 alkyl groups, more preferred C1 -C6 alkyl groups, even more preferred C1 -C4 alkyl groups. Additionally, it has to be understood that the additives might react with the surface of the metal effect pigment. Furthermore, it has to be understood that the terminal oxygen atom of the alkoxy chain (Alk)_n is binding to the phosphor. Naturally, the oxygen atom of the alkoxy group is not bound to the oxygen atom bridging the R¹ group of formula (I) establishing a peroxo bond. Furthermore, it has to be understood that in case multiple cationic counter ions are available within in paste the calculation of the wt.-% of the at least one additive is based on the lightest counter ions available. If a specific group of counter ions is selected as specified hereafter, the lightest counter ion is selected among those. It has to be understood that the amounts of the components of the metal effect pigment paste as specified and optionally included like, for example, rheology modifiers sum up to 100 wt.-%, based on the weight of the metal effect pigment paste. Naturally, the summed total weight of all components of the paste has to be the weight of the paste itself.

Further preferred embodiments of the metal effect pigments pastes according to the present invention are located, for example, in claims 2 to 17 or aspects 2 to 28.

Furthermore, the present invention refers to a method of producing a metal effect pigment paste, wherein the method comprises the following steps:

a) providing a metal effect pigment paste in a solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof,

b) optionally mixing at least one additive according to formula (I):

wherein the R¹ are independently from each other selected from C9-C30 aliphatic groups,

Alk is selected from group consisting of ethoxy, propoxy and mixtures thereof, the R² are independently from each other selected from the group consisting of H, C1 -C4 alkyl groups and cationic counter ions,

n is a number in the range of 3 to 100 and represents the number averaged value of the number of alkoxy units,

x is 1 or 2,

with a solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, butyl acetate and mixtures thereof, and

c) addition of at least one additive according to formula (I) to the paste and mixing the composition. Examples of solvents used in step b) are solvent naphtha, white spirit and butyl acetate.

Further preferred embodiments of the method according to the present invention are located, for example, in claims 19 to 21 or aspects 30 to 62.

Furthermore, the present invention refers to a metal effect pigment paste prepared according to the inventive method. Preferred embodiments are located in, for example, aspect 64.

Furthermore, the present invention refers to an use of an inventive metal effect pigment paste in a plastic material or a coating composition like solvent borne automotive coatings and industrial coatings such as can & coil coatings. Examples of said coating formulations are solvent borne automotive coatings and industrial coatings such as can & coil coatings.

Further preferred embodiments of the use according to the present invention are located, for example, in aspect 66.

Furthermore, the present invention refers to a coating composition comprising the inventive metal effect pigment paste. Preferably such coating composition is selected from the group consisting of solvent borne automotive coatings and industrial coatings such as can & coil coatings.

Furthermore, the present invention refers to an object comprising the inventive metal effect pigment.

The term„metal effect pigment" according to the present invention refers to platy metal pigments. Preferably such pigments provide an aspect ratio of at least 10, more preferably of at least 20. The term "aspect ratio" according to the present invention describes the ratio of the average particle size (d₅o) and the average particle thickness (h₅₀) = (dso/hso)- The term„d₅₀" or„d₅o-value"within the meaning of the present invention denotes the particle size at which 50% of the particles provide a particle size smaller or equal to according to the volume-averaged particle-size distribution as determined using laser granulometry. The measurements are preferably carried out with the particle-size analyzer HELOS from

Sympatec GmbH , Clausthal-Zellerfeld, Germany. Dispersing of the dry powder may be carried out using a dispersing unit Rodos T4.1 using a primary pressure of, for example, 4 bar. Alternatively the particle size of the particles may be, for example, carried out using a Cilas 1064 from Quantachrome. Herein, the manufacturers' instructions may be used for measurement. In this context, 1 .5 g of the powdery coating material are dispersed in around 100 ml ethanol and treated for 300 seconds using ultrasonic sound using, for example, a Sonorex I K52 from Bandelin. Thereafter, it may be transferred to the measurement device using a Pasteur pipette and measured several times resulting in the averaged particle size. The analysis of the scattered light signals is performed using the Fraunhofer method.

The thicknesses of the particles may be performed using, for example, SEM. For this purpose the particles are first washed with aceton and dried. Then a typical resin as used for scanning electron microscope (SEM) like TEMPFIX from Gerhard Neubauer Chemikalien, D- 48031 Mijnster, Germany is placed in a sample plate and heated until it softens. In the following, the heating is stopped and the particles are scattered on the softened resin. Based on the cooling down the resin resolidifies and the scattered particles are - based on the interplay of adhesion and gravity - prepared standing vertically. Based thereon the side face of the particles may be measured very well using SEM. When measuring the thicknesses the azimuthal angle a of the particles to the surface of the normal layer is estimated and included in the analysis of the thicknesses of the particles using the following formula:

h_eff = hmes/COSOt

, wherein h_etf represents the real thickness and h_mes represents the measured thickness. Based on the h_eff-values the sum distribution curve is created. For this purpose around 100 particles, preferably 100 particles, are measured. The sum distribution curve can also be designated as cumulative frequency curve.

If the aforementioned method of measuring is not applicable the thicknesses of the particles might also be determined using cross-section polishes of lacquered samples. This method, however, should only be used in case of very well plane-parallel oriented particles.

Otherwise, particles might be wrongly measured providing a greater thickness based on their azimuthal angle. Surprisingly, it has been found that the inventive metal effect pigment pastes provide significantly improved long term storage stability. This remarkable finding is very surprising as a polar additive as specified by formula (I) should provide low to no solubility in nonpolar organic solvents itself. In particular, it should not increase the storage stability of a metal effect pigment paste in such solvent.

Even more surprisingly it has been noted that further benefits are observed. For example, it has been noted that metal effect pigment pastes known in the art comprising other additives are prone to a significant yellowing of corresponding varnish systems. However, the additive of the inventive metal effect pigment pastes did surprisingly not provide such disadvantage.

Additionally, it has been noted that the inventive metal effect pigment pastes provide a very beneficial texture. Namely, the compact texture of the inventive metal effect pigment pastes provide a good stability as well as an easy processing of the metal effect pigment paste in further processing steps. It has even been noted that it was typically not required to introduce a dispersing additive in a further step before introducing the inventive metal effect pigments pastes into a coating composition. Even the orientation in wet coating compositions does not only seem to be maintained but even seems to be slightly improved in typical test systems.

In the following the essential components of the inventive metal pigment paste will be described in further detail.

The term„polymer" as used in the present invention also comprises oligomers. However, preferably the polymers comprise are least 10, more preferred at least 20, even more preferred at least 60 monomer units.

The terms "Cx-Cy" according to the present invention refer to the range of carbon atoms in the specified groups. For example, a C1 -C4 alkyl group may contain 1 , 2, 3 or 4 carbon atoms. Examples of such alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec- butyl, isobutyl and tert-butyl.

As long as not specified otherwise it is especially preferred that the term "essentially" according to the present invention has the meaning of at least 95 %, more preferred of at least 98 %, even more preferred of at least 99 %. If it refers to a material property like the amount of a component it refers to wt.-%. Furthermore, it has to be noted that the ranges as specified in the present invention include the end points of said ranges unless explicitly specified otherwise. For example, if m is a number in the range of 6 to 15 the end points 6 and 15 are included.

Unless specified otherwise aliphatic groups or compounds, alkyl groups or compounds and aromatic groups or compounds are unsubstituted.

The term "brass" according to the present invention refers to alloys consisting essentially of copper and zinc, wherein copper represents at least 50 wt.-% of the alloy.

Component A) metal effect pigment:

The metal effect pigments as specified under A) of the inventive metal effect pigment paste provide a d₅o-value in the range of 5 μηη to 80 μηι, preferably in the range of 5 μηη to 66 μηι, more preferred in the range of 5.7 μηη to 51 μηη, even more preferred in the range of 7.2 μηη to 47 μηη. Such Pigments proved to be very useful, for example, for visual effects.

According to further embodiments of the invention the metal effect pigments provide an h₅₀ value of the thickness distribution curve in the range of 140 to 800 nm.

Although, the metal of the metal effect pigments is not necessarily restricted the inventive metal effect pigment paste formulation proved to be especially useful for certain metal effect pigments. According to further embodiments of the present invention the metal of the metal effect pigments consists essentially of a metal being selected from the group consisting of aluminum, copper, iron, zinc, silver, alloys thereof like steel or brass, and mixtures thereof. The term "alloy thereof" as used in the present invention refers to a mixture of metals comprising at least 50 wt.-%, more preferred at least 65 wt.-%, of the specified metal.

According to further embodiments the metal of the metal effect pigments consists to at least 95 wt.-%, more preferred at least 98 wt.-%, even more preferred at least 99 wt.-% of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel and brass, and mixtures thereof, based on the weight of the metal of the metal effect pigment excluding oxygen of a optionally metal oxide layer being an oxidation product of the surface of said metal effect pigment.

According to further embodiments of the present invention the metal of the metal effect pigments preferably consists essentially of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel or brass, and mixtures thereof, more preferred selected from the group consisting of aluminum, copper, brass, aluminum alloys comprising at least 80 wt.-% aluminum, based on the weight of the metal of the aluminum alloy pigment, and mixtures thereof.

The inventive metal effect pigment paste proved to be especially useful for metal effect pigments, wherein the metal of the metal effect pigments essentially consists of aluminum or alloys thereof.

According to further embodiments of the present invention the metal of the metal effect pigments comprises at most 5 wt.-%, more preferred at most 2 wt.-%, even more preferred at most 1 wt.-%, of a metal selected from the group consisting of silver, palladium, platin, gold and mixtures thereof, based on the weight of the metal of the metal effect pigments.

The metal effect pigments as used in the present invention may be prepared according to typical methods known to the person skilled in the art. For example, they may be prepared using milling processes of metal powder, especially aluminum powder, copper powder or iron powder. Furthermore, such metal effect pigments can be prepared using physical vapor deposition (PVD). It has to be noted that the methods of preparation like the two methods mentioned above are able to provide strongly differing pigments, for example, providing different qualities and properties and requiring different types of further processing and handling.

The metal effect pigments may be coated or uncoated. Herein, it is especially preferred that such optional coating is located below the inventive additive as specified according to the present invention. According to further preferred embodiments of the present invention the metal effect pigments are selected from the group consisting of uncoated metal effect pigments, coated pigments, wherein the coating consists essentially, preferably completely, of an organic polymer, and mixtures thereof. In further embodiments the metal effect pigments are essentially either uncoated or coated pigments, wherein the coating consists essentially, preferably completely, of an organic polymer.

According to one especially preferred embodiment uncoated metal effect pigments are used. The term "uncoated" according to the present invention refers to pigments not providing any at least essentially enveloping, preferably enveloping, coating around the metal core of the metal effect pigment. Such at least essentially enveloping coatings are typically highly cross- linked to provide a strong protection against external substances. Examples of such coatings are metal oxide coatings or polymer coatings. Naturally, such uncoated metal effect pigments may still comprise substances like grinding additives such as stearic acid or oleic acid on their surfaces.

In further embodiments at least 90 wt.-%, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments are selected from uncoated metal effect pigments, based in each case on the total weight of the metal effect pigments.

According to a very preferred embodiment of the present invention all metal effect pigments are uncoated metal effect pigments. These pastes are very popular in certain applications, as they typically combine high grade visual effects with low cost, although, they are far more restricted when choosing, for example, the coating system or the components of the coating composition. Such metal effect pigments are, for example, preferably used in solvent borne coating formulations.

In other cases, however, the pigments should be protected to at least a certain degree against influences of the environment or chemicals used, for example, in the coating compositions. According to further embodiments of the present invention the metal effect pigments are essentially selected from coated metal effect pigments, wherein the coating consists essentially, preferably completely, of an organic polymer. Such layer provides a protection against other substances, especially corrosive substances, comprised in the metal effect pigment paste or, for example, in a coating composition the metal effect pigment paste is introduced into.

According to other embodiments it is preferred that at least 90 wt.-%, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments comprise an organic polymer coating, based in each case on the total weight of the metal effect pigments. Preferably, all metal effect pigments are metal effect pigments comprising an organic polymer coating.

According to further embodiments of the present invention the organic polymer coating provides an average thickness in the range of preferably 100 nm to 300 nm, more preferred in the range of 120 nm to 250 nm and even more preferred in the range of 150 nm to

230 nm. It has been observed that below an average thickness of 100 nm the protective properties have typically been reduced. On the other hand an average thickness of more than 300 nm typically resulted in a reduction of the covering capacity and/or the luster of the metal effect pigments. According to further embodiments of the present invention the amount of the organic polymer coating is preferably at least 8 wt.-%, more preferred at least 9.5 wt.-%, even more preferred at least 10 wt.-%, even more preferred at least 1 1 wt.-%, based in each case on the weight of the uncoated metal effect pigment.

According to further embodiments of the present invention the amount of the organic polymer coating is preferably at most 40 wt.-%, more preferred at most 35 wt.-%, even more preferred at most 30 wt.-%, even more preferred at most 23 wt.-%, based in each case on the weight of the uncoated metal effect pigment.

In further preferred embodiments of the present invention the amount of the organic polymer coating lies preferably in the range of 8 wt.-% to 40 wt.-%, more preferred in the range of 9,5 wt.-% to 35 wt.-%, even more preferred in the range of 10 wt.-% to 23 wt.-%, even more preferred in the range of 1 1 wt.-% to 23 wt.-%, based in each case on the weight of the uncoated metal effect pigment.

Furthermore, it has been noted that specific organic polymers might be especially beneficially used for coating the metal effect pigments. According to further preferred embodiments the organic polymer is selected from the group consisting of polyacrylate, polymethacrylate, polyacrylamide, polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, polyamide, polyalkene, polydiene, polyalkyne, polyalkylene glycol, epoxy resin, polyester, polyether, polyol, polyurethane, polycarbonate, polyethylene terephthalate and mixtures thereof, more preferred from the group consisting of polyacrylate, polymethacrylate, polyurethane, polyester and mixtures thereof.

In particular embodiments of the present invention the organic polymer is selected from the group consisting of polyacrylates, polymethacrylates and mixtures thereof. These polymers provide, for example, an improved UV-resistance.

Examples of monomeric acrylates that might be used for coating the metal effect pigments include, for example, isoamyl acrylate, lauryl acrylate, stearyl acrylate, butoxyethyl acrylate, ethoxy diethylene glycol acrylate, methoxy triethylene glycol acrylate, methoxy polyethylene glycol acrylate, methoxy dipropylene glycol acrylate, phenoxyethyl acrylate, phenoxy polyethylene glycol acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1 ,6-hexanediol diacrylate, 1 ,9- nonanediol diacrylate, dimethylol tricyclodecane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, 2- hydroxy-3-acryloyloxy propyl methacrylate, isooctyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethyl hexyl diglycol acrylate, 2-hydroxybutyl acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, hydroxy pivalic acid neopentyl glycol diacrylate, polytetraethylene glycol diacrylate, ditrimethylolpropane tetraacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecyl

methacrylate, n-lauryl methacrylate, tridecyl methacrylate, n-stearyl methacrylate, methoxydiethylene glycol methacrylate, methoxy polyethylene glycol methacrylate, cyclohexyl methacrylate, tetrahydrofurfural methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, isobornyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-methacryloyloxyethyl succinic acid, 2- methacryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1 ,4-butanediol dimethacrylate, 1 ,3-butanediol dimethacrylate, 1 ,6-hexanediol dimethacrylate, 1 ,9- nonanediol dimethacrylate, trimethylolpropane trimethacrylate, glycerol dimethacrylate, 2- hydroxy-3-acryloyloxy propyl methacrylate, t-butyl methacrylate, isostearyl methacrylate, methoxytriethylene glycol methacrylate, n-butoxyethyl methacrylate, 3-chloro-2- hydroxypropyl methacrylate, triethylene glycol dimethacrylate, neopentyl glycol

dimethacrylate.

It further proved useful including at least one monomer comprising at least two, particularly preferably at least three, reactive double bonds. Such monomers result in a cross linking and increase the strength of the organic polymer coating. Examples of such monomers are 1 ,6- hexanediol diacrylate, 1 ,9-nonanediol diacrylate, dimethyloltricyclodecanediacrylate neopentyl glycol dimethacrylate trimethylolpropane triacrylate and trimethylolpropane trimethacrylate.

Another group of organic polymers that might be beneficially used is the group consisting of polyamide, polycarbonate, polyvinyl chloride, polyethylene terephthalate and mixtures thereof. Such organic polymer coatings, for example, typically provide increased temperature stability.

Component B) additive:

The inventive composition provides at least one additive according to formula (I):

wherein the R¹ are independently from each other selected from C9-C30 aliphatic groups, Alk is selected from group consisting of ethoxy, propoxy and mixtures thereof,

the R² are independently from each other selected from the group consisting of H, C1 -C4 alkyl groups and cationic counter ions,

x is 1 or 2.

Surprisingly, it has been noted that metal effect pigment compositions did not provide the required long term storage stability if additives have been used, wherein R¹ provides less than 9 C atoms. Furthermore, if R¹ was longer than 30 C-atoms the metallic pastes exhibited leafing properties which are not desired according to the present invention. According to further embodiments of the present invention the R¹ are independently from each other selected from C10-C20 aliphatic groups, more preferred selected from C1 1 -C14 aliphatic groups.

Surprisingly, it was further noted that the usage of linear or branched aliphatic groups seems to provide beneficial effects like a slightly decreased agglomeration in certain formulations.

In further embodiments of the present invention the R¹ are independently from each other selected from C9-C30 alkyl groups, more preferred C10-C20 alkyl groups, more preferred a C1 1 -C14 alkyl groups. An especially preferred R¹ is a-isotridecyl.

It is the opinion of the inventors without being bound to that theory that the additive binds to the surface of the metal effect pigment by means of its phosphoric acid group.

Simultaneously, R¹ is directed away from the metal pigment surface and provides just enough steric hindrance to prevent agglomeration of the metal effect pigments in the paste.

In further embodiments of the present invention the number of ethoxy units of structural element (Alk)_n of the at least one additive is at least the equal to the amount of the C atoms of R¹, more preferred at least the 1.5 fold of the amount of C atoms of R¹, even more preferred at least twice of the amount of the C atoms of R¹, based in each case on the number averaged value of the number of ethoxy units and the total number of C atoms of the R¹. According to further embodiments of the present invention the number averaged value of the number of alkoxy units n of the at least one additive according to formula (I) is preferably in the range of 5 to 50, more preferred in the range of 6 to 25, even more preferred in the range of 7 to 10.

According to further preferred embodiments of the present invention the structural element (Alk)n is a block polymer either consisting completely of ethoxy units or consisting essentially of block units of at least three, more preferred of at least 5, even more preferred of at least 7 units. The term "block units" according to the present invention refers to a chain consisting of only either ethoxy or propoxy units. Preferably such block copolymer consists of at least 95 wt.-%, more preferred at least 98 wt.-%, of such block units, based on the total weight of the alkoxy units.

Furthermore, it has been noted that especially beneficial results, for example, for typical formulations have been obtained using additives providing a higher ratio of ethoxy units. In further embodiments at least 50 wt.-%, preferably at least 65 wt-%, of the alkoxy units are ethoxy units, based in each case on the total weight of the alkoxy groups. Preferably, the alkoxy chain (Alk)_n consists essentially of ethoxy units, more preferred to at least 95 wt.-% of ethoxy units, even more preferred to at least 99 wt.-% of ethoxy units, based in each case on the total weight of the alkoxy groups. According to an especially preferred embodiment (Alk)_n consists of ethoxy groups.

In further embodiments of the present invention at least one R², preferably all R², of the at least one additive according to formula (I) is selected from the group consisting of H, C1 -C4 alkyl groups and (NH₄)⁺. Such additives proved to be beneficial, as, for example,

corresponding metal effect pigment pastes comprising said counter ions could be introduced into a great variety of coating formulations without any problems. Without being bound to any theory it is the opinion of the inventors that at least certain alkyl ammonium counter ions might interact with components of certain coating composition.

According to further preferred embodiments of the present invention at least one R², preferably all R², of the at least one additive according to formula (I) is H. Without being bound to a theory, it is the understanding of the inventors that the presence of at least on phosphoric acid group is beneficial in most cases.

According to further embodiments the at least one additive provides an acid number of at least 75 mg KOH/g, more preferred of at least 85 mg KOH/g, even more preferred of at least 90 mg KOH/g. The acid number is measured using typical procedures known to the person skilled in the art. For example, it may be measured using titration based upon a KOH-solution or NaOH-solution, wherein the end point of the titration is determined, for example, using a pH indicator or an electrode like Ag/AgCI, preferably using an electrode. Such method is described, for example, in DIN EN ISO 21 14.

In further embodiments the at least one additive according to formula (I) provides an acid number of at most 130 mg KOH/g, more preferred of at most 120 mg KOH/g, even more preferred of at most 1 10 mg KOH/g.

According to further preferred embodiments of the present invention the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g, more preferred in the range of 85 mg KOH/g to 120 mg KOH/g, even more preferred in the range of 90 mg KOH/g to 1 10 mg KOH/g.

According to some very preferred embodiments of the present invention the metal effect pigment paste comprises

A) 55 to 70 wt.-% metal effect pigments, based on the total weight of the metal effect pigment paste, wherein the metal is aluminum or alloys thereof, with a d₅₀-value in the range of 5 μηη to 80 m

B) 0.2 to 10 wt.-% of at least one additive according to formula (II), based on the weight of the metal effect pigments,

[R³-0-(CH₂-CH₂-0)_m]_y-P(=0)(OH)_3-y (II), wherein the R³ are independently from each other selected from C1 1 -C15 linear or branched aliphatic groups,

m is a number in the range of 6 to 15 and represents the number averaged value of the number of alkoxy units and

y is 1 or 2. Preferably R³ is a C10-C15 alkyl group.

In some very preferred embodiments of the present invention the metal effect pigment paste provides 0.2 to 10 wt.-% of at least one additive according to formula (II), based on the weight of metal effect pigment, wherein R³ is a C13 alkyl group and y is 1 or 2, preferably 1 . According to further preferred embodiments of the present invention the R¹ of the at least one additive according to formula (I) are independently from each other selected from C10-C20 alkyl groups,

at least 50 wt.-%of the alkoxy units of (Alk)_n of the at least one additive are ethoxy units, based on the total weight of the alkoxy groups, and

the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g.

Such additives are commercially available under the trade names: Hostaphat 1306,

Hostaphat 1308, Dispersogen XP 060 (all available by Clariant), Beyrostat A 136,Rhodafac RS/710,Servoxyl VPDZ 20/100, Servoxyl VPDZ 6/100 or Servoxyl VPDZ 9/100 (available from Elementis Specialities). For example, Servoxyl VPDZ 20/100 is an additive according to formula (I), wherein R¹ is isotridecyl, Alk is ethoxy and n is around 20.

The additives as used in the present invention are commercially available and, of course, may be produced using standard methods of chemistry. For example, these additives might be prepared in a multistep procedure first preparing the structural element R1 -0-(Alk)n-OH followed by coupling said substance or its derivative with phosphoric acid or its derivatives. Such reaction might beneficially employ phosphoric trichloride. The structural element R1 -0- (Alk)n-OH on the other hand can be prepared by means, for example, of a coupling reaction of R1 -X and the alkoxychain (Alk)n. The alkoxychain (Alk)n is available, for example, using a condensation reaction of ethylene glycol and/or propylene glycol. Herein, a mixture of ethoxy and propoxy units or a sequence of block units might be acquired. Furthermore, it is possible to first prepare multiple block units of either ethoxy or propoxy groups and couple these units to prepare the alkoxy chain (Alk)n. The reaction between R1 -X and (Alk)n might also be a simple condensation reaction or, for example, an aliphatic halogenide might be reacted with the hydroxy group of the alkoxy chain (Alk)n. These and many more synthetic routes to prepare the additives used in the present invention are well known to the person skilled in the art.

C) Solvent:

Solvents used in the metal effect pigment paste essentially consist of nonpolar solvents selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof. According to further embodiments the specified solvents essentially consist of aliphatic hydrocarbons like alkanes. Examples of such solvents are white spirit, solvent naphtha and mixtures thereof. These solvents are usually used during the production of metal effect pigments like aluminum pigments by the Hall process known for many decades. Furthermore, grinding aids are typically employed like fatty acids such as oleic acid, stearic acid or mixtures thereof. Grinding aids like fatty acids should prevent cold shuts during the milling process. They are typically present in every conventional metal effect pigment paste in amounts of typically 0.3 to 2 wt.-%, based on the metal pigment. The exact amount may depend on the specific surface area of the metal pigment.

According to further embodiments at least 85 wt-% of the solvents of C), more preferred at least 92 wt.-% of the solvents of C), even more preferred at least 96 wt.-%of the solvents of C), even more preferred all solvents of C), based in each case on the total weight of the solvents of C), are selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof, more preferred from the group consisting of alkanes, aromatic hydrocarbons and mixtures thereof. Examples of such solvents are, for example, sold under names like white spirit, mineral spirit and solvent naphtha.

In further embodiments at least 60 wt.-% of the solvents of C), more preferred at least 75 wt- % of the solvents of C), even more preferred at least 90 wt.-% of the solvents of C), based in each case on the total weight of the solvents of C), are selected from aliphatic hydrocarbons. According to further embodiments they are preferably selected from alkanes.

Especially preferred groups of aliphatic hydrocarbons that might be used according to the present invention are C6-C20 aliphatic hydrocarbons, more preferred C7-C17 aliphatic hydrocarbons, even more preferred C8-C16 aliphatic hydrocarbons. Preferably, the aliphatic hydrocarbons are selected from the corresponding alkanes. The alkanes especially include linear, branched and cyclic alkanes.

Especially preferred groups of aromatic hydrocarbons that might be used according to the present invention are C6-C12 aromatic hydrocarbons, more preferred C6-C1 1 aromatic hydrocarbons, even more preferred C6-C10 aromatic hydrocarbons.

According to further preferred embodiments the aromatic hydrocarbons are preferably selected from the group of alkylated benzenes, wherein the alkyl groups are preferably selected from C1 -C3 alkyl groups, even more preferred from C1 -C2 alkyl groups, especially methyl. Examples of such aromatic hydrocarbons are toluene and xylenes.

In further embodiments of the present invention the amount of the solvents of C) is at least 26 wt.-%, more preferred at least 29 wt.-%, based in each case on the total weight of the metal effect pigment paste In further embodiments of the present invention the amount of the solvents of C) is at most 42 wt.-%, more preferred at most 40 wt.-%, even more preferred at most 39 wt.-%, based in each case on the total weight of the metal effect pigment paste

Paste:

The inventive metal effect pigment paste comprising the components A), B) and C) may contain further components such as anti-settling agents, rheology modifier and anti-foaming agents.

Such further components, however, shall preferably not be contained in high amounts, preferably not more than 2 wt.-%, even more preferred not more than 1 wt.-%, based on the total weight of the metal effect pigment paste excluding solvents. However, preferably the aforementioned upper limits are based on the total weight of the metal effect pigment paste including the solvents.

According to further preferred embodiments the inventive metal effect pigment paste does not contain any glass frit. The term "glass frit" according to the present invention refers to fine glass powder. Examples of such glass powder are used in the electronic industry. It is especially preferred that the inventive metal effect pigment paste does not contain any glass frit providing a softening point of at most 700 °C, more preferred at most 630 °C.

According to further embodiments the metal effect pigment paste consists preferably essentially of components A), B) and C). Preferably the amount of components A), B) and C) is at least 90 wt.-%, more preferred at least 95 wt.-%, even more preferred 98 wt.-%, even more preferred at least 99 wt.-%, based in each case on the total weight of the metal effect pigment paste. In a further preferred embodiment the components A), B) and C) amount to 100 wt.-% of the metal effect pigment paste.

Although, the amount of the additive at least one additive in the inventive metal effect pigment paste might vary within 0.2 to 10 wt.-% it is preferred according to further embodiments that the inventive metal effect pigments pastes comprise the at least one additive in an amount from 0.3 wt.-% to 7 wt.-%, more preferred from 0.35 wt.-% to 5 wt.-%, even more preferred from 0.4 wt.-% to 4 wt.-%, based in each case on the weight of the metal effect pigments. In further specifically preferred embodiments of the present invention the metal of the metal effect pigments of A) consists essentially of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel or brass, and mixtures thereof, the R¹ of the at least one additive according to formula (I) are independently from each other selected from C10-C20 alkyl groups,

at least 50 wt.-%of the alkoxy units of (Alk)_n of the at least one additive are ethoxy units, based on the total weight of the alkoxy groups,

the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g,

at least 92 wt.-% of the solvents of C), based on the total weight of the solvents of C), are selected from the group consisting of aliphatic hydrocarbons, preferably alkanes, aromatic hydrocarbons and mixtures thereof, and

the amount of components A), B) and C) is at least 90 wt.-% based on the total weight of the metal effect pigment paste. Preferably, such metal effect pigment paste does not contain any glass frit.

According to another variant the present invention refers to a method of producing metal effect pigment pastes.

In further embodiments of the present invention the metal pigments are provided in step a) in a solvent essentially consisting of a solvent being selected from the preferred aliphatic hydrocarbons and aromatic hydrocarbons as specified with regard to the inventive paste like from the group consisting of C6-C20 aliphatic hydrocarbons, C6-C12 aromatic hydrocarbons and mixtures thereof.

Furthermore, it is preferred according to further embodiments that the aliphatic hydrocarbons and aromatic hydrocarbons used in the optional step b) of the inventive method are selected from the preferred aliphatic hydrocarbons and aromatic hydrocarbons as specified with regard to the inventive paste.

It is very preferred according to the present invention that the metal effect pigments, the at least one additive and the solvents used in the inventive method are selected from those disclosed for the metal effect pigment pastes.

In further embodiments of the present invention the ratio of the at least one additive : solvent in step b) is in the range of 1 :2 to 2:1 , more preferred in the range of 2:3 to 3:2, based in each case on the weight of the substances. The mixing of step c) might be performed using, for example, a milling device or a mechanical stirrer. Employing a milling device provides, for example, the benefit that such process step might be added directly after a milling process to produce said metal effect pigments. Such process provides a typically highly cost efficient production process eliminating a following process step. However, such optimized production process requires certain adjustment according to the substances and metal pigments used. Furthermore, it might be problematic if multiple different products have to be produced on the same machine and a cross contamination has to be avoided. Such process is especially beneficial for large scale products. For products, for example, produced in smaller scale that require a certain flexibility or prevent any cross contamination it proved to be more efficient using some mechanical stirring device or a comparable device in a separated step.

Preferably the inventive method is used to produce a metal effect pigment paste as disclosed herein.

According to further embodiments of the present invention step c) of the inventive method is followed by a step d), wherein the amount of solvent is reduced. Such step might be used to obtain a highly concentrated paste or a powder, wherein a powder is especially preferred according to specific embodiments. Herein, typical methods known to the person skilled in the art might be used. For example, the solvents might be removed by heating, using low pressure or a combination thereof.

Removing at least the major part of the solvent provides, for example, benefits when transporting said metal effect pigment composition. Surprisingly, such inventive powders maintained their beneficial properties and could easily be redispersed in the solvents as specified herein typically without any noticeably decrease with regard to the inventive effects or, for example, their optical properties. Naturally, metal effect pigment types like PVD- pigments are much more sensitive towards, for example, agglomeration and, thus, an at least slight decrease is difficult to avoid. However, surprisingly the decrease with regard to the optical or other properties was surprisingly small. According to further embodiments of the present invention the metal effect pigments and the at least one additive according to formula (I) amount to at least 93 wt.-%, more preferred to at least 96 wt.-%, even more preferred to at least 98 wt.-%, based in each case on the total weight of the metal effect pigment composition. According to another variant the present invention refers to a metal effect pigment composition produced by the inventive method or its embodiments. Such composition preferably is in the form of a powder or a paste. Pastes provide, for example, an easy processability and avoid, for example dusting. Powders, however, provide, for example, a simplified transport or storage.

According to another variant the present invention refers to the use of an inventive metal effect pigment paste like, for example, specified in claim 23 or aspects 65 to 66 in a plastic material or a coating composition. Examples of such coating compositions are non-aqueous coating compositions like solvent borne automotive coatings, powder coatings and can-/coil coatings. Furthermore, the inventive metal effect pigment paste might be used to prepare a master batch used for plastic material or for powder coating.

According to further embodiments of the present invention the inventive metal effect pigment pastes are used in a solvent borne coating formulation.

According to another variant the present invention refers to a plastic material or a coating composition comprising the inventive metal effect pigment paste. Such coating composition can be, for example, selected from the group consisting of solvent borne automotive coatings and industrial coatings such as can & coil coatings.

According to another variant the present invention refers to objects comprising the inventive metal effect pigment paste or a product thereof.

According to further embodiments of the present invention it is especially preferred to introduce the inventive metal effect pigment paste into a coating composition and apply the resulting coating composition onto the surface of an object.

Furthermore, the inventive metal pigment paste might be introduced into a plastic material used in the object or used for coating said object.

According to an aspect 1 the present invention refers to a metal effect pigment paste, wherein the metal effect pigment paste comprises:

x is 1 or 2,

According to an aspect 2 the present invention refers to the metal effect pigment paste according to aspect 1 , wherein the metal effect pigments preferably provide a d₅₀-value in the range of 5 μηη to 66 μηη, more preferred in the range of 5.7 μηη to 51 μηη, even more preferred in the range of 7.2 μηη to 47 μηη.

According to an aspect 3 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 2, wherein the metal effect pigments preferably provide an h₅₀ value of the thickness distribution curve in the range of 140 to 800 nm.

According to an aspect 4 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 3,wherein the metal of the metal effect pigments preferably consists essentially of a metal being selected from the group consisting of aluminum, copper, iron, zinc, silver, alloys thereof like steel or brass, and mixtures thereof. According to further embodiments the metal of the metal effect pigments consists to at least 95 wt.-%, more preferred at least 98 wt.-%, even more preferred at least 99 wt.-% of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel and brass, and mixtures thereof, based on the weight of the metal of the metal effect pigment excluding oxygen of a optionally metal oxide layer being an oxidation product of the surface of said metal effect pigments.

According to an aspect 5 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 4,wherein the metal of the metal effect pigments preferably consists essentially of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel or brass, and mixtures thereof, more preferred selected from the group consisting of aluminum, copper, brass, aluminum alloys comprising at least 80 wt.-% aluminum, based on the weight of the metal of the aluminum alloy pigment, and mixtures thereof.

According to an aspect 6 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 5, wherein the metal of the metal effect pigments preferably essentially consists of aluminum or alloys thereof.

According to an aspect 7 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 6, wherein preferably at least 90 wt.-%, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments are uncoated metal effect pigments, based in each case on the total weight of the metal effect pigments. Preferably all metal effect pigments are uncoated metal effect pigments.

According to an aspect 8 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 7, wherein preferably at least 90 wt.-%, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments comprise an organic polymer coating, based in each case on the total weight of the metal effect pigments. Preferably, all metal effect pigments are metal effect pigments comprising an organic polymer coating.

According to an aspect 9 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 8, wherein preferably the organic polymer coating is selected from polyacrylate, polymethacrylate, polyurethane, polyester and mixtures thereof.

According to an aspect 10 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 9,wherein preferably the number of ethoxy units of structural element (Alk)_n of the at least one additive is at least the equal to the amount of the C atoms of R¹, more preferred at least the 1.5 fold of the amount of C atoms of R¹, even more preferred at least twice of the amount of the C atoms of R¹, based in each case on the number averaged value of the number of ethoxy units and the total number of C atoms of the R¹. According to an aspect 1 1 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 10,wherein preferably the R¹ of the at least one additive are independently from each other selected from C9-C30 alkyl groups.

According to an aspect 12 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 1 1 ,wherein preferably (Alk)_n of the at least one additive consists to at least 50 wt.-% of ethoxy units, more preferred at least 65 wt.-% of ethoxy units, based on the total weight of the alkoxy groups.

According to an aspect 13 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 12, wherein preferably (Alk)_n of the at least one additive consists essentially of ethoxy units, more preferred to at least 95 wt.-% of ethoxy units, even more preferred to at least 99 wt.-% of ethoxy units, based in each case on the total weight of the alkoxy groups. According to an especially preferred embodiment (Alk)_n consists of ethoxy groups.

According to an aspect 14 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 13, wherein preferably R¹ of the at least one additive is a linear or branched aliphatic group.

According to an aspect 15 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 14, wherein preferably the R¹ of the at least one additive are independently from each other selected from C10-C20 aliphatic groups, more preferred C1 1 - C14 aliphatic groups, even more preferred are a-isotridecyl.

According to an aspect 16 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 15, wherein preferably n of the at least one additive is a number in the range of 5 to 50, more preferred in the range of 6 to 25.

According to an aspect 17 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 16, wherein preferably at least one, more preferred all, R² of the at least one additive are H.

According to an aspect 18 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 17, wherein preferably the at least one additive according to formula (I) provides an acid number of at least 75 mg KOH/g, more preferred of at least 85 mg KOH/g, even more preferred of at least 90 mg KOH/g. According to an aspect 19 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 18, wherein preferably the at least one additive according to formula (I) provides an acid number of at most 130 mg KOH/g, more preferred of at most 120 mg KOH/g, even more preferred of at most 1 10 mg KOH/g.

According to an aspect 20 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 19, wherein preferably the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g, more preferred in the range of 85 mg KOH/g to 120 mg KOH/g, even more preferred in the range of 90 mg KOH/g to 1 10 mg KOH/g.

According to an aspect 21 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 20, wherein preferably at least 85 wt-% of the solvents of C), more preferred at least 92 wt.-% of the solvents of C), even more preferred at least 96 wt.- %of the solvents of C), even more preferred all solvents of C), based in each case on the total weight of the solvents of C), are selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof.

According to an aspect 22 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 21 , wherein preferably at least 60 wt.-% of the solvents of C), more preferred at least 75 wt.-% of the solvents of C), even more preferred at least 90 wt.-% of the solvents of C), based in each case on the total weight of the solvents of C), are selected from aliphatic hydrocarbons. Preferably, the aliphatic hydrocarbons are alkanes.

According to an aspect 23 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 22, wherein the aliphatic hydrocarbons are preferably selected from C6-C20 aliphatic hydrocarbons, more preferred C7-C17 aliphatic

hydrocarbons, even more preferred C8-C16 aliphatic hydrocarbons. Preferably, the aliphatic hydrocarbons are selected from the corresponding alkanes.

According to an aspect 24 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 23, wherein the aromatic hydrocarbons are preferably selected from C6-C12 aromatic hydrocarbons, more preferred C6-C1 1 aromatic

hydrocarbons, even more preferred C6-C10 aromatic hydrocarbons. According to an aspect 25 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 24, wherein the aromatic hydrocarbons are preferably selected from alkylated benzenes, wherein the alkyl groups are preferably selected from C1 - C3 alkyl groups, even more preferred from C1 -C2 alkyl groups, especially methyl.

According to an aspect 26 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 25, wherein preferably the total weight of components A), B) and C) is at least 90 wt.-%, more preferred at least 95 wt.-%, even more preferred 98 wt.-%, even more preferred at least 99 wt.-%, based in each case on the total weight of the metal effect pigment paste. In a further preferred embodiment components A), B) and C) amount to 100 wt.-% of the metal effect pigment paste.

According to an aspect 27 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 26, wherein preferably the paste does not contain any glass frit.

According to an aspect 28 the present invention refers to the metal effect pigment paste according to any of aspects 1 to 27,wherein preferably the metal effect pigment paste comprises

y is 1 or 2.

According to an aspect 29 the present invention refers to a method of producing a metal effect pigment paste, wherein the method comprises the following steps:

b) optionally mixing at least one additive according to formula (I):

x is 1 or 2,

According to an aspect 30 the present invention refers to the method of producing a metal effect pigment paste according to aspect 29, wherein preferably step b) is conducted at a temperature from 15 to 35 °C.

According to an aspect 31 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 30, wherein preferably the metal pigments are provided in step a) in a solvent essentially consisting of a solvent being selected from the group consisting of C6-C20 aliphatic hydrocarbons, C6-C12 aromatic hydrocarbons and mixtures thereof.

According to an aspect 32 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 31 , wherein preferably the ratio of the at least one additive: solvent in step b) is in the range of 1 :2 to 2:1 , more preferred in the range of 2:3 to 3:2, based in each case on the weight of the substances.

According to an aspect 33 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 32, wherein preferably the metal effect pigments provide a d₅₀-value in the range of 5 μηη to 66 μηη, more preferred in the range of 5.7 μηη to 51 μηη, even more preferred in the range of 7.2 μηη to 47 μηη. According to an aspect 34 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 33, wherein preferably the metal effect pigments provide a h₅₀ value of the thickness distribution curve in the range of 140 to 800 nm.

According to an aspect 35 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 34, wherein preferably the metal of the metal effect pigments consists essentially of a metal being selected from the group consisting of aluminum, copper, iron, zinc, silver, alloys thereof like steel or brass, and mixtures thereof. The term "alloy thereof" according to the present invention refers to a mixture of metals comprising at least 50 wt.-%, more preferred at least 65 wt.-%, of the specified metal. According to further embodiments the metal of the metal effect pigments consists to at least 95 wt.-%, more preferred at least 98 wt.-%, even more preferred at least 99 wt.-% of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel and brass, and mixtures thereof, based on the weight of the metal of the metal effect pigment excluding oxygen of a optionally metal oxide layer being an oxidation product of the surface of the metal effect pigments.

According to an aspect 36 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 35, wherein preferably the metal of the metal effect pigments consists essentially of a metal selected from the group consisting of aluminum, copper, iron, zinc, alloys thereof like steel or brass, and mixtures thereof, more preferred selected from the group consisting of aluminum, copper, brass, aluminum alloys comprising at least 80 wt.-% aluminum, based on the weight of the metal of the aluminum alloy pigment, and mixtures thereof.

According to an aspect 37 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 36, wherein preferably the metal of the metal effect pigments essentially consists of aluminum or alloys thereof.

According to an aspect 38 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 37, wherein preferably at least 90 wt- %, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments are uncoated metal effect pigments, based in each case on the total weight of the metal effect pigments. Preferably all metal effect pigments are uncoated metal effect pigments. According to an aspect 39 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 38, wherein preferably at least 90 wt- %, more preferred at least 97 wt.-%, even more preferred at least 99 wt.-% of the metal effect pigments comprise an organic polymer coating, based in each case on the total weight of the metal effect pigments. Preferably, all metal effect pigments are metal effect pigments comprising an organic polymer coating.

According to an aspect 40 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 39, wherein preferably the organic polymer coating is selected from polyacrylate, polymethacrylate, polyurethane, polyester and mixtures thereof.

According to an aspect 41 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 40, wherein preferably the number of ethoxy units of structural element (Alk)_n of the at least one additive is at least the equal to the amount of the C atoms of R¹, more preferred at least the 1 .5 fold of the amount of C atoms of R¹, even more preferred at least twice of the amount of the C atoms of R¹, based in each case on the number averaged value of the number of ethoxy units and the total number of C atoms of the R¹.

According to an aspect 42 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 41 , wherein preferably the R¹ of the at least one additive are independently from each other selected from C9-C30 alkyl groups.

According to an aspect 43 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 42, wherein preferably (Alk)_n of the at least one additive consists to at least 50 wt.-%, more preferred at least 65 wt.-%, of ethoxy units, based on the total weight of the alkoxy groups. Preferably all additives according provide such structural element (Alk)_n.

According to an aspect 44 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 43, wherein preferably (Alk)_n of the at least one additive consists essentially, more preferred to at least 95 wt.-%, even more preferred to at least 99 wt.-%, of ethoxy groups, based in each case on the total weight of the alkoxy groups. According to an especially preferred embodiment (Alk)_n consist of ethoxy groups. According to an aspect 45 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 44, wherein preferably R¹ of the at least one additive is a linear or branched aliphatic group.

According to an aspect 46 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 45, wherein preferably the R¹ of the at least one additive are independently from each other selected from C10-C20 aliphatic groups, more preferred C1 1 -C14 aliphatic groups, even more preferred are a-isotridecyl.

According to an aspect 47 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 46, wherein preferably n of the at least one additive is a number in the range of 5 to 50.

According to an aspect 48 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 47, wherein preferably at least one, more preferred all, R² of the at least one additive are H.

According to an aspect 49 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 48, wherein preferably the at least one additive according to formula (I) provides an acid number of at least 75 mg KOH/g, more preferred of at least 85 mg KOH/g, even more preferred of at least 90 mg KOH/g.

According to an aspect 50 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 49, wherein preferably the at least one additive according to formula (I) provides an acid number of at most 130 mg KOH/g, more preferred of at most 120 mg KOH/g, even more preferred of at most 1 10 mg KOH/g.

According to an aspect 51 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 50, wherein preferably the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g, more preferred in the range of 85 mg KOH/g to 120 mg KOH/g, even more preferred in the range of 90 mg KOH/g to 1 10 mg KOH/g.

According to an aspect 52 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 51 , wherein preferably the obtained metal effect pigment paste comprises:

A) 55 to 70 wt.-% metal effect pigments, based on the total weight of the metal effect pigment paste, with a d₅o-value in the range of 5 μηι to 80 μηι

x is 1 or 2,

According to an aspect 53 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 52, wherein preferably at least 85 wt- % of the solvents of C), more preferred at least 92 wt.-% of the solvents of C), even more preferred at least 96 wt.-%of the solvents of C), even more preferred all solvents of C), based in each case on the total weight of the solvents of C), are selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof.

According to an aspect 54 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 53, wherein preferably at least 60 wt- % of the solvents of C), more preferred at least 75 wt.-% of the solvents of C), even more preferred at least 90 wt.-% of the solvents of C), based in each case on the total weight of the solvents of C), are selected from aliphatic hydrocarbons. Preferably, the aliphatic hydrocarbons are alkanes.

According to an aspect 55 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 54, wherein the aliphatic

hydrocarbons are selected from C6-C20 aliphatic hydrocarbons, more preferred C7-C17 aliphatic hydrocarbons, even more preferred C8-C16 aliphatic hydrocarbons. Preferably, the aliphatic hydrocarbons are selected from the corresponding alkanes. According to an aspect 56 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 55, wherein the aromatic

hydrocarbons are preferably selected from C6-C12 aromatic hydrocarbons, more preferred C6-C1 1 aromatic hydrocarbons, even more preferred C6-C10 aromatic hydrocarbons.

According to an aspect 57 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 56, wherein the aromatic

hydrocarbons are preferably selected from alkylated benzenes, wherein the alkyl groups are preferably selected from C1 -C3 alkyl groups, even more preferred from C1 -C2 alkyl groups, especially methyl.

According to an aspect 58 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 57, wherein preferably the total weight of components A), B) and C) is at least 90 wt.-%, more preferred at least 95 wt.-%, even more preferred 98 wt.-%, even more preferred at least 99 wt.-%, based on the total weight of the metal effect pigment paste. In a further preferred embodiment components A), B) and C) amount to 100 wt.-% of the metal effect pigment paste.

According to an aspect 59 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 58, wherein preferably the obtained paste does not contain any glass frit.

According to an aspect 60 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 59, wherein preferably the obtained metal effect pigment paste comprises

y is 1 or 2.

According to an aspect 61 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 60, wherein preferably the method includes a step d) following step c), wherein the amount of solvent is reduced. Preferably, a powder is obtained in step d).

According to an aspect 62 the present invention refers to the method of producing a metal effect pigment paste according to any of aspects 29 to 61 , wherein preferably the metal effect pigments and the at least one additive according to formula (I) amount to at least 93 wt.-%, more preferred to at least 96 wt.-%, even more preferred to at least 98 wt.-%, based in each case on the total weight of the composition.

According to an aspect 63 the present invention refers to a metal effect pigment composition prepared according to the method of any of aspects 29 to 62.

According to an aspect 64 the present invention refers to the method of producing a metal effect pigment paste according to aspect 63, wherein preferably such composition is in the form of a powder or a paste.

According to an aspect 65 the present invention refers to an use of a metal effect pigment paste according to one of the aspects 1 to 28 or a metal effect pigment composition according to any of aspects 63 to 64 in a plastic material or a coating composition like solvent borne automotive coatings and industrial coatings such as can & coil coatings. Examples of said coating formulations are solvent borne automotive coatings and industrial coatings such as can & coil coatings.

According to an aspect 66 the present invention refers to the use according to aspect 65,wherein preferably the coating composition is a solvent borne coating formulation.

According to an aspect 67 the present invention refers to a coating composition comprising a metal effect pigment paste according to any of aspects 1 to 28 or a metal effect pigment composition according to any of aspects 63 to 64. According to an aspect 68 the present invention refers to a coating composition of aspect 67, wherein the coating composition is selected from the group consisting of solvent borne automotive coatings and industrial coatings such as can & coil coatings.

According to an aspect 69 the present invention refers to an object comprising a metal effect pigment paste according to any of aspects 1 to 28 or a metal effect pigment composition according to any of aspects 63 to 64.

Examples:

Application example 1 : Texture of metal effect pigment pastes

The aim of the present invention was to provide a metal effect pigment paste with very good storage stability, good optical properties, no yellowing and a compact consistency. In preselection tests 50 g of Siltallic 8080 (60 wt.-% aluminium effect pigment, 40 wt.-% of a mixture of C8-C15 alkanes) (d₅₀ = 12 μηη) have been mixed with a mixture consisting of 1 part by weight of solvent naphtha and one part by weight of the additive as specified in Table 1 . Herein, the concentration of the resulting metal effect pigment paste was 1 wt.-% or 2 wt.- %, based on the weight of the aluminum pigment. The textures of the pastes were evaluated qualitatively by their visual appearance.

Table 1 : Textures of metal effect pigments pastes comprising various additives.

e: example; ce: comparative example

Most of these additives lead to loosely pigment preparations which did not have the typical paste behavior. Only the additive of example 1 -1 leads to satisfactory paste textures.

Comparable results to example 1 -1 have been furthermore achieved using Lubrhophos

LB400 (oleyl alcohol, around 27 ethoxy units, mono ester), Rhodafac PA35 (oleyl alcohol, around 27 ethoxy units, mono ester), Rhodafac PA 23 (C10-C14 alcohol, around 30 ethoxy units, mono ester), Rhodafac RS/710 (C13 alcohol, around 27 ethoxy units, mono ester), Rhodafac MB (C10-C14 alcohol, around 27 ethoxy units, ester mixture), Servoxyl VPDP 20/35 (C13-alcohol, around 20 ethoxy units, potassium salt), Servoxyl VPFZ 7/100 (oleyl alcohol, around 7 ethoxy units, ester mixture), Servoxyl VPBZ 5/100 (C12-C18 alcohol, around 5 ethoxy units, ester mixture), Sodium salt of Servoxyl VPDZ 20/100 (C13-alcohol, around 20 ethoxy units), potassium salt of Rhodafac RS/710, sodium salt of Rhodafac PA 23, sodium salt of Servoxyl VPBZ 5/100, and potassium salt of Rhodafac LB400. Such pastes also greatly differed in their optical properties and appeared much brighter. The additives providing a satisfactory consistence of the paste have been further tested with regard to their resistance against yellowing.

The inventive metal effect pigment pastes as well as a corresponding metal effect pigment paste without additive are introduced into a standard OEM clear base coat test system (PPG). Herein, the weight ratio of metal pigment : varnish was 1 :4. The resulting coating compositions are applied on a plain metal substrate panel (approx. 10X20cm) using an automatic spray painting machine from Kohne GmbH in Wuppertal, Germany. The spray gun used is a SATA LP JET MSB LAB spray gun including a MSB nozzle 1 .4, wherein a pressure of 5 bar is employed. The applied coating provides a wet thickness of around 100 μηη.

Hereafter, a standard clear coat (PPG) is applied providing a wet thickness of 80 μηη. The coated metal substrates are placed into an oven and heated to 140 °C for 25 min. Thereafter, the color of the provided coating is measured using a BYK-mac using the CieLab model at 5 reflection angles (15°, 25°, 45°, 75°, 1 10°). For fulfilling the requirements the average fa- value (5 samples) measured at 45° of the inventive paste including the additive had to differ less than 0.6 from the average b-value (5 samples) of the reference pastes without additive.

Surprisingly, the pastes containing the inventive additives provided the required resistance against yellowing being a typical problem of such pastes.

Application example 2: Long term storage stability tests

In various tests it was observed that additives not leading to a compact texture did not provide the required long term storage stability of corresponding aluminum metal effect pastes.

Without being bound to a theory it is believed that if the pastes had a rather loosely texture air could more easily penetrate into the pigment preparation. Therefore, oxygen reaches the surfaces of the aluminum pigments much earlier leading to oxidation of fatty acids and/or the pigment surface which results finally in the formation of agglomerates. If, however, the aluminum pigment paste provides a compact appearance the solvent seems to be bound and homogenized much better leading to a strongly reduced penetration of air into the paste. Exemplary the following tests results are presented.

Various grades of different aluminum pastes (70 wt.-% aluminium effect pigment, 30 wt.-% of a mixture of C8-C15 alkanes) have been mixed with the additives as specified in the table below. The pastes obtained were stored in an oven at 50 °C. To pass the test the

corresponding sample should provide no agglomeration after four weeks.

The occurrence of agglomeration was tested by drawing samples of the metal paste in the oven and incorporating these into a standard test system (yellow lacquer, BASF Coatings) at various concentrations. Drawdowns of these lacquers were prepared 100 μηη. The hiding power was visually evaluated at day light and in comparison to a metal paste of the same type not stored in the oven without addition of further additives. In addition the drawdowns were visually inspected with respect to the occurrence of spots or humps.

Table 2: Long term storage stability tests

e: example; ce: comparative example

The metal effect pigment pastes obtained are furthermore introduced into a standard solvent borne base coat (acrylic, PE, melamin varnish base coat) resulting in a solid content of the varnish system of 20 wt.-%. A solvent mixture (1 :1 mixture by weight of xylene and butyl acetate) is added to provide a fluidity of around 18 s DIN 4 cup. This varnish is applied to a plain metal substrate panel (approx. 10X20cm) using an automatic spray painting machine from Kohne GmbH in Wuppertal, Germany, with a SATA LP JET MSB LAB spray gun using a MSB nozzle 1 .4 at 5 bar. The applied film has a wet thickness of around 100 μηη. After 10 min a layer of a standard clear coat (isocyanate blocked PU, acrylate, high bake) providing a wet thickness of 80 μηη is applied. The coated metal substrates are placed into an oven and heated to 140 °C for 25 min. The optical properties have been determined using a BYK-mac based on the CieLab model at 5 reflection angles.

Table 2: Application tests of the stored metal effect pigment pastes

The comparison of inventive examples and corresponding comparative examples (e 2-3, ce 2-4, e 2-5 and ce 2-6) shows an improvement of the inventive examples with regard to brightness (L15°) and flop index.

Application example 3: Texture of metal effect pigment pastes

Additional types of metal pigments have been tested according to the procedure as described under application example 1 . Namely, different aluminum effect pigments (Stapa 22 n.l.), copper effect pigments (Stapa Resist AT copper), iron effect pigments (Stapa TA Ferricon 200), zinc pigments (Stapa Zinc flake GTT), and brass effect pigments (Standart Lac E900 pale gold).

Herein, the aforementioned pigments have been reformulated as pastes containing 60 wt.-% solid content and 40 wt.-% of a mixture of C8-C15 alkanes accordingly to the paste used in application example 1. Thereafter, the pastes have been tested using the additive of example 1 -1 . The obtained pastes provided comparable results with regard to the resulting pasty behavior. Furthermore, the aluminum, iron and zinc effect pigments provided the resistance against yellowing as disclosed in Application example 1. The copper and brass effect pigments have not been tested in this context.

Claims

1. Metal effect pigment paste, wherein the metal effect pigment paste comprises:

x is 1 or 2,

2. Metal effect pigment paste according to claim 1 , wherein the metal of the metal effect pigments consists essentially of a metal being selected from the group consisting of aluminum, copper, iron, zinc, silver, alloys thereof and mixtures thereof.

3. Metal effect pigment paste according to any of claims 1 to 2, wherein the metal of the metal effect pigments essentially consists of aluminum or alloys thereof.

4. Metal effect pigment paste according to any of claims 1 to 3, wherein at least 97 wt- % of the metal effect pigments are uncoated metal effect pigments, based on the total weight of the metal effect pigment paste.

5. Metal effect pigment paste according to any of claims 1 to 4, wherein the number of ethoxy units of structural element (Alk)_n of the at least one additive is at least the equal to the amount of the C atoms of R¹, based on the number averaged value of the number of ethoxy units and the total number of C atoms of the R¹.

6. Metal effect pigment paste according to any of claims 1 to 5, wherein the R¹ of the at least one additive are independently from each other selected from C9-C30 alkyl groups.

7. Metal effect pigment paste according to any of claims 1 to 6, wherein (Alk)_n of the at least one additive consists to at least 65 wt.-% of ethoxy units, based on the total weight of the alkoxy groups.

8. Metal effect pigment paste according to any of claims 1 to 7, wherein (Alk)_n of the at least one additive consists essentially of ethoxy units, based on the total weight of the alkoxy groups.

9. Metal effect pigment paste according to any of claims 1 to 8, wherein the R¹ of the at least one additive are independently from each other selected from C10-C20 aliphatic groups.

10. Metal effect pigment paste according to any of claims 1 to 9, wherein n of the at least one additive is a number in the range of 5 to 50.

1 1 . Metal effect pigment paste according to any of claims 1 to 10, wherein at least one R² of the at least one additive is H.

12. Metal effect pigment paste according to any of claims 1 to 1 1 , wherein the at least one additive according to formula (I) provides an acid number in the range of 75 mg KOH/g to 130 mg KOH/g.

13. Metal effect pigment paste according to any of claims 1 to 12, wherein at least 92 wt- % of the solvents of C, based on the total weight of the solvents, are selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof.

14. Metal effect pigment paste according to any of claims 1 to 13, wherein at least 60 wt.- % of the solvents of C), based on the total weight of the solvents of C), are selected from aliphatic hydrocarbons.

15. Metal effect pigment paste according to any of claims 1 to 14, wherein the total weight of components A), B) and C) is at least 90 wt.-%, based on the total weight of the metal effect pigment paste.

16. Metal effect pigment paste according to any of claims 1 to 15, wherein the paste does not contain any glass frit.

17. Metal effect pigment paste according to any of claims 1 to 16, wherein the metal effect pigment paste comprises

A) 55 to 70 wt.-% metal effect pigments, based on the total weight of the metal effect pigment paste, wherein the metal is aluminum or alloys thereof, with a d₅₀-value in the range of 5 μηη to 80 μηι

y is 1 or 2.

18. Method of producing a metal effect pigment paste, wherein the method comprises the following steps:

a) providing an metal effect pigment paste in a solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and mixtures thereof,

b) optionally mixing at least one additive according to formula (I):

x is 1 or 2,

c) addition of at least one additive according to formula (I) to the paste and mixing the composition.

19. Method of producing a metal effect pigment paste according to claim 18, wherein step b) is conducted at a temperature from 15 to 35 °C.

20. Method of producing a metal effect pigment paste according to any of claims 18 to 19, wherein the metal pigments are provided in a solvent essentially consisting of a solvent being selected from the group consisting of C6-C20 aliphatic hydrocarbons, C6-C12 aromatic hydrocarbons and mixtures thereof.

21 . Method of producing a metal effect pigment paste according to any of claims 18 to 20, wherein the ratio of the at least one additive : solvent in step b) is in the range of 1 :2 to 2:1 , based on the weight of the substances.

22. Metal effect pigment composition prepared according to the method of any of claims 18 to 21 .

23. Use of a metal effect pigment paste according to any of the claims 1 to 17 or a metal effect pigment composition according to claim 22 in a plastic material or a coating

composition.